[GSoC] StackGAN Model

[Vishal-V]

• StackGAN model implementation as part of GSoC 2019 proposal.
• The model has been implemented from the paper.
• The code follows the recommended python guidelines and is compatible with the TF 2.0 beta release.
• The code has been tested and all bugs have been fixed for both Stage 1 and Stage 2 of the StackGAN.
• The architecture list is present in the README file and all dependencies can be downloaded from the requirements.txt file.